A study of Cl2/BCl3-based inductively coupled plasma (ICP) was conducted usingthick photoresist mask for anisotropic etching of 50 μm diameter holes in a GaAs wafer at arelatively high average etching rate for etching depths of more than 150 μm. Plasma etch characteristicswith ICP process pressure and the percentage of BCl_3 were studied in greater detailat a constant ICP coil/bias power. The measured peak-to-peak voltage as a function of pressurewas used to estimate the minimum energy of the ions bombarding the substrate. The processpressure was found to have a substantial influence on the energy of heavy ions. Various ion speciesin plasma showed minimum energy variation from 1.85 eV to 7.5 eV in the pressure range of20 mTorr to 50 mTorr. The effect of pressure and the percentage of BCI3 on the etching rate andsurface smoothness of the bottom surface of the etched hole were studied for a fixed total flow rate.The etching rate was found to decrease with the percentage of BCI3, whereas the addition of BCl_3resulted in anisotropic holes with a smooth veil free bottom surface at a pressure of 30 mTorr and42% BCl_3. In addition, variation of the etching yield with pressure and etching depth were alsoinvestigated. A study of Cl2 / BCl3-based inductively coupled plasma (ICP) was conducted using a thin film photoresist for anisotropic etching of 50 μm diameter holes in a GaAs wafer at are relatively high average etching rate for etching depths of more than 150 μm. process pressure and the percentage of BCl_3 were studied in greater detailat a constant ICP coil / bias power. The measured peak-to-peak voltage as a function of pressurewas used to estimate the minimum energy of the ions bombarding the substrate. The processpressure was found Various ion speciesin plasma showed minimum energy variation from 1.85 eV to 7.5 eV in the pressure range of 20 mTorr to 50 mTorr. The effect of pressure and the percentage of BCI3 on ​​the etching rate and surface smoothness of the bottom surface of the etched hole were studied for a fixed total flow rate. The etching rate was found to decrease with the percentage of BCI3, wherea s the addition of BCl_3resulted in anisotropic holes with a smooth veil free bottom surface at a pressure of 30 mTorr and 42% BCl_3.In addition, variation of the etching yield with pressure and etching depth were also also investigated.